Slit coater  having apparatus for supplying a coater solution

ABSTRACT

A slit coater including an apparatus for supplying coating solution by a coating method using a slit nozzle, which is configured to minimize contamination of coating solution, utilizing a filtering function, and supplying a controlled amount of photosensitive solution to a slit nozzle. The slit coater further includes a table on which an object to be processed is mounted, a slit nozzle unit that applies coating solution onto a surface of the object to be processed, and a coating solution supply apparatus including a storage tank that stores the coating solution, a pump that supplies the coating solution stored in the storage tank to the slit nozzle unit, and a buffer tank that is in fluid communication with the pump and the storage tank.

RELATED APPLICATIONS

This patent document is a divisional application and claims the benefitpursuant to 35 U.S.C. § 121 of U.S. application Ser. No. 11/211,257filed on Aug. 19, 2005, which has been allowed and is herebyincorporated in its entirety by reference. This application also claimsthe benefit of priority to Korean Patent Application 114395/2004, filedon Dec. 28, 2004, herein incorporated in its entirety by reference.

TECHNICAL FIELD

The present invention relates, generally, to a slit coater and, moreparticularly, to a slit coater capable of uniformly supplying a coatingsolution to a nozzle that applies a coating solution, such as aphotosensitive solution, development solution, or a color filter onto anobject to be processed such as a glass substrate, a semiconductor wafer,or the like, of a flat panel display (FPD) device.

BACKGROUND

When a flat panel display device or a semiconductor device isfabricated, a process for depositing a thin film, a photolithographyprocess for exposing a region selected in the thin film and an etchingprocess for removing the thin film of the selected region are performedseveral times. Particularly, the photolithography process includes acoating process for forming a photosensitive film of a photosensitivesolution such as a photoresist on a substrate or a wafer, and anexposing and developing process for patterning the photosensitive filmby using a mask with a predetermined pattern.

In general, a spray coating method, a roll coating method, a spincoating method or the like is used in the coating process for forming aphotosensitive film on a substrate and a wafer.

Because the spray coating method and the roll coating method are notsuitable to achieve high precision in the uniformity of a coating filmand the adjustment of a thickness of the film, the spin coating methodis used for high-precision pattern formation.

A spin coater used in the spin coating method will now be described indetail with reference to accompanying drawings.

FIG. 1 is a sectional view which illustrates the structure of a generalspin coater.

As shown, the spin coater includes a spin chuck 5 that is connected to arotating shaft 6. A cover 7 surrounds the spin chuck 5 and can be openedand closed. A nozzle 4 is placed above the spin chuck 5 and moves intothe cover 7 when the cover 7 is opened.

An object 10 to be processed and coated with a photosensitive film ismounted on the spin chuck 5, and a drain valve (not shown) fordischarging photosensitive solution, such as photoresist, to the outsideis installed at a lower portion of the cover 7.

In order to form a coating film on the predetermined object 10 to beprocessed, first, the nozzle 4 of the spin coater having theaforementioned structure is lowered and sprays photosensitive solutiononto a surface of the object 10, which has been placed on the spin chuck5.

When the photosensitive solution is sprayed onto the object 10, thecover 7 is hermetically closed, a motor (M) is rotated, and the rotatingshaft 6 connected thereto is rotated, thereby rotating the spin chuck 5with the object 10 a certain number of times.

When the spin chuck 5 is rotated, the photosensitive solution on thesurface of the object 10 is spread out by a centrifugal force, therebyapplying the photosensitive solution over an entire surface of theobject 10.

After the photosensitive solution is applied over the entire surface ofthe object 10, the applied photosensitive solution is hardened. Then, apredetermined pattern is formed on the surface of the object 10 throughexposure and development using a photo mask or the like.

Although the spin coating method using the spin coater is suitable tocoat a small object, such as a wafer with a photosensitive film, it isnot suitable to coat a large and heavy substrate, such as a flat paneldisplay device having a glass substrate for a liquid crystal displaypanel with a photosensitive film.

This is because it gets harder to rotate a substrate at a high speed asthe substrate gets larger and heavier. Further, damage to the substratecan occur and much energy is consumed when the substrate is rotated at ahigh speed.

Also, the spin coating method is disadvantageous in that a large amountof photosensitive solution is wasted in comparison with the amount ofphotosensitive solution used in the photolithography process. Inparticular, a considerable amount of photosensitive solution isdispersed outside the spin chuck at the time of high-speed rotation, andis wasted. Substantially, the amount of wasted solution is much largerthan the amount of solution used for coating, and the dispersedphotosensitive solution may form particles that contaminate followingthin film forming processes. The particles can also cause environmentalpollution.

BRIEF SUMMARY

In accordance with the present invention there is provided a slit coaterhaving an apparatus for supplying coating solution, including a table onwhich an object to be processed is mounted; a slit nozzle unitconfigured to apply a coating solution onto a surface of the object; anda coating solution supply apparatus including a storage tank configuredto store the coating solution, a pump that supplies the coating solutionstored in the storage tank to the slit nozzle unit, and a buffer tank influid communication with the pump and the storage tank, wherein thesupply apparatus substantially uniformly maintains pressure of the pumpand removes bubbles from the coating solution.

In accordance with another aspect of the invention, a coating systemincludes a slit nozzle unit configured to apply a coating solution ontoa surface of an object; a coating solution storage tank; a coatingsolution supply system that includes a pump; a buffer tank in fluidcommunication with the pump and the storage tank, wherein the coatingsolution supply system is configured to supply a substantially uniformamount of coating solution at a substantially uniform pressure from thebuffer tank to the slit nozzle unit.

The foregoing and other features, aspects, and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute aunit of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a sectional view which illustrates a structure of a relatedart spin coater;

FIGS. 2A and 2B are perspective views which illustrate a slit coater andapplication of photosensitive solution by the slit coater in accordancewith an embodiment of the invention;

FIG. 3 is a schematic exemplary view which illustrates a slit coaterhaving an apparatus for supplying photosensitive solution in accordancewith a first embodiment of the present invention; and

FIG. 4 is a schematic exemplary view which illustrates a slit coaterhaving an apparatus for supplying photosensitive solution in accordancewith a second embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

In general, as mentioned above, a photolithography process is requiredin the field of semiconductor manufacture and the field of flat paneldisplay device in order to pattern a thin film performing a specificfunction, for example, an insulation film, a metal thin film, asemiconductor thin film or the like, into a desired form. Here,photosensitive solution such as photoresist, which chemically reacts tolight, is used in the photolithography process.

A photosensitive film having a uniform thickness should be formed on asubstrate on which a thin film has been formed, so that a defect doesnot occur during a process. For example, if the photosensitive film hasa thickness greater than a designated thickness, a portion of the thinfilm which should be etched is not etched, and if the photosensitivefilm has a thickness smaller than the designated thickness, the thinfilm is excessively etched. Also, the uniform application of thephotosensitive solution is one of the most important issues as thesubstrate becomes larger due to an increase in size of the liquidcrystal display panel of a liquid crystal display (LCD) device.

In accordance with an embodiment of the invention, a nozzle method inwhich a certain amount of photosensitive solution is sprayed by using aslit nozzle is employed in place of a prior art spinner. A coatingapparatus employing such a nozzle method is referred to as a spinlesscoater because a spinner is not used. Alternatively, the term “slitcoater” is used because photosensitive solution is sprayed through aslit. The slit coater supplies the photosensitive solution through anozzle having a slit shape with a length longer than its width, andapplies the photosensitive solution onto a surface of a substrate in aplane form, which makes the slit coater suitable to apply thephotosensitive solution to a large LCD device.

FIGS. 2A and 2B are exemplary views which illustrate a slit coater andthe application of a photosensitive solution by the slit coater. Inaccordance with an embodiment of the invention, the slit coater isprovided with a nozzle 22 having a narrow and long slit. Photosensitivesolution 30 is supplied through the slit nozzle 22, thereby applying thephotosensitive solution 30 on a surface of a substrate 100 in a planeform.

The slit coater is an apparatus that applies a predetermined amount ofphotosensitive solution 30 onto the substrate 100 or the like through abar-shaped long slit nozzle 22. The slit coater applies a uniform amountof photosensitive solution 30 through a fine slit nozzle 22, moving fromone side to the other side of the substrate 100 at a constant speed,thereby forming a uniform photosensitive film on the surface of thesubstrate 100.

Also, because the slit coater can apply the photosensitive solution 30only to a desired surface of the substrate 100, the coating solution canbe used without being wasted as compared to the aforementioned spincoater. In addition, because the slit coater can apply the coatingsolution in a plane form with a long width, it is suitable for a largesubstrate or a quadrangular substrate.

For reference, element 40 indicates a table on which the substrate 100is mounted, and the arrow indicates a direction in which thephotosensitive solution 30 is sprayed and applied along a direction thatthe slit nozzle 22 moves.

The slit coater in accordance with the present invention is providedwith an apparatus that supplies photosensitive solution to the nozzle ofthe slit coater, and this will now be described in detail with referencethe accompanying drawing.

FIG. 3 is a schematic exemplary front view of a slit coater providedwith the apparatus for supplying photosensitive solution in accordancewith the first embodiment of the present invention.

As shown, the slit coater in accordance with the present embodimentincludes a table 140 on which a substrate 100 is mounted, a slit nozzleunit 120 that applies coating solution, for example, photosensitivesolution such as photoresist, onto the substrate 100, and a driving unit150 that is installed at both ends of the slit nozzle unit 120 and movesthe slit nozzle unit 120 at a constant speed.

The driving unit 150 includes a pair of Z-axial driving apparatuses 151installed at both ends of the slit nozzle unit 120 and moving the slitnozzle unit 120 in a vertical direction, and a pair of Y-axial drivingapparatuses 152 moving the slit nozzle unit 120 back and forth to allowthe photosensitive solution to be uniformly sprayed on the surface ofthe substrate 100.

Here, each Y-axial driving apparatus 152 may include a motor (not shown)and a transfer unit (not shown) such as a transfer rail and a guiderail, and a non-contact type linear motor can be used as the motor.

An object 100 to be processed such as a glass substrate is mounted onthe table 140, and a plurality of pins 141 for lifting up the substrate100 from the table 140 are installed inside the table 140. The pins 141are supported by a plate 142 placed under the table 140, and mounts orlifts the object 100 on or from the table 140 by action of the plate 142that is, in turn, moved up and down by a driving unit (not shown) suchas a motor.

Although not shown in the drawing, a preliminary discharge apparatus forapplying a initial coating may be installed at one side of the table140.

The slit nozzle unit 120 includes a slit type nozzle 122 that is placedabove the substrate 100 and across the substrate 100 and has a lengthcorresponding to a width of the substrate 100, and a head 121 to whichthe nozzle 122 is mounted.

Although not shown in detail, the nozzle 122 includes a nozzle body, aninlet and an outlet, wherein the nozzle body has a receiving space forstoring a photosensitive solution therein, the inlet is formed at thenozzle body, and the outlet is formed at a surface of the nozzle body,which faces the substrate 100. Here, the outlet has a slit shape havinga length longer than its width.

Also, the nozzle 122 sprays the photosensitive solution, while movingfrom one side to the other side of the substrate 100 through the Y-axialdriving apparatuses 152, thereby uniformly applying the photosensitivesolution on the surface of the substrate 100. The photosensitivesolution may also be applied by sliding the substrate 100 relative tothe nozzle 122, which remains in a fixed position.

A bubble outlet 160 for removing bubbles within the nozzle 122 residesat an upper end of the head 121 of the slot nozzle unit 120.

The slit coater having such a structure further includes a supplyapparatus for supplying photosensitive solution to the nozzle 122 of theslit nozzle unit 120, and a storage tank 171 for storing photosensitivesolution. The supply apparatus also includes a supply line 176 throughwhich the stored photosensitive solution is supplied to the slit nozzleunit 120, and a flow control unit such as a sensor 190. The supplyapparatus further includes a pumping unit such as a pump 172 thatprovides the photosensitive solution to be sprayed by applying constantpressure to the photosensitive solution being supplied from the storagetank 171 to the slit nozzle unit 120.

The storage tank 171 stores coating solution such as a photosensitivesolution, for example, a photoresist, development solution, a colorfilter, or the like, that is to be supplied to the slit nozzle unit 120.The storage take 171 may be attached to the driving unit 150.

A buffer tank 175 is installed between the pump 172 and the storage tank171 in order to make the pressure of the pump 171 constant and removebubbles. A level sensor 190 for measuring the amount of residualphotosensitive solution is attached to the buffer tank 175.

In the illustrated arrangement, the level sensor 190 of the buffer tank175 detects a shortage of the photosensitive solution and sends a signalto a control apparatus (not shown), and the control apparatus sends thesignal to a sixth valve 180F to allow clean and dry air to be introducedto the storage tank 171, thereby introducing the photosensitive solutionwithin the storage tank 171 into the buffer tank 175.

In the illustrated embodiment, the buffer tank 175 is placed atsubstantially the same height as the pump 172 so as to minimize pressuredifference due to potential energy, and a hole, namely, an air passage185 is made at one side of an upper end of the buffer tank 175, therebyalways maintaining constant pressure of the buffer tank 175. By mountingan air filter at the air passage 185, contamination within the buffertank 175 can be minimized.

The pressure generated by photosensitive solution introduced to thebuffer tank 175 is eliminated by the air passage 185, so that the buffertank 175 can be filled with the photosensitive solution. Here, in astate that a second valve 180B is opened and third and fifth valves 180Cand 180E are closed, the photosensitive solution is drawn into the pump172 from the buffer tank 172. Accordingly, the intake amount is notvaried.

In a state that the second and fifth valves 180B and 180E are closed andthe third valve 180C is opened for an initiation signal of a coatingprocess, the photosensitive solution drawn into the pump 172 isdischarged to the surface of the substrate 100 through the slit nozzle122.

If air bubbles are formed in the pump 172, the fifth valve 180E isopened in while the third and second valves 180C and 180B are closed,thereby removing the bubbles and thusly minimizing variations in thedischarge amount due to the bubbles. If the bubbles are formed in theslit nozzle 122, the fourth valve 180D is opened so that the bubbles canbe discharged through the bubble discharge outlet 160.

As the photosensitive solution is drawn into the pump 172 whileatmospheric pressure is maintained, such that the internal pressure ofthe pump 172 can be constant every time the suction is performed, whichallows the pump 172 to always draw a certain amount of photosensitivesolution and thusly discharge a fixed amount of photosensitive solution.

A filter 170 for removing impurities from the photosensitive solutionbeing supplied from the storage tank 171 is installed between the buffertank 175 and the storage tank 171.

However, in the photosensitive supply apparatus in accordance with thefirst embodiment, because the buffer tank 175 is placed downstream ofthe filter 170 and the buffer tank 175 is always opened to be in theatmospheric state, an environment where the air is likely to come intocontact with the photosensitive solution is provided, which can causethe photosensitive solution to be polluted and to form a gel.

FIG. 4 is a schematic exemplary view which illustrates a slit coaterhaving an apparatus for supplying photosensitive solution in accordancewith the second embodiment.

The slit coater in accordance with the present embodiment has the samestructure as that of the slit coater in accordance with the firstembodiment, except for the configuration of the apparatus for supplyingphotosensitive solution.

As shown, the slit coater in accordance with the present embodimentincludes a table 240 on which a substrate 200 is mounted, a slit nozzleunit 220 that applies coating solution, for example, photosensitivesolution such as photoresist, on the substrate 200, and a driving unit250 which is installed at both ends of the slit nozzle unit 220 andmoves the slit nozzle unit 220 at a constant speed.

The driving unit 250 includes a pair of Z-axial driving apparatuses 251installed at both ends of the slit nozzle unit 220 and moving the slitnozzle unit 220 up and down, and a pair of Y-axial driving apparatuses252 that moves the slit nozzle unit 220 back and forth at a constantspeed and uniformly sprays the photosensitive solution on the surface ofthe substrate 200.

An object 200 to be processed such as a glass substrate is mounted onthe table 240, and a plurality of pins 241 for lifting up the substrate200 from the table 240 are installed inside the table 200. The pins 241are supported by a plate 242 placed under the table 240, therebymounting or lifting the substrate 200 on or from the table 240 bymovement of the plate 242 vertically through action of a driving unit(not shown) such as a motor.

The slit nozzle unit 220 is placed above and across the substrate 200and includes a nozzle 222 having a slit shape with a lengthcorresponding to a width of the substrate 200, and a head 221 to whichthe nozzle 222 is mounted.

The nozzle 222 sprays photosensitive solution, moving from one sidetoward the other side of the substrate 220 through the Y-axial drivingapparatus 252, thereby uniformly applying a photosensitive solution onthe surface of the substrate 200.

The nozzle 222 sprays photosensitive solution, moving from one sidetoward the other side of the substrate 220 through the Y-axial drivingapparatus 252, thereby uniformly applying a photosensitive solution onthe surface of the substrate 200.

The slit coater having such a structure further includes a supplyapparatus for supplying a uniform amount of photosensitive solution in astate that the contamination of the photosensitive solution is minimizedand a filtering function is utilized to the maximum extent. The supplyapparatus includes a storage tank 271 for storing photosensitivesolution, a supply line 276 through which the photosensitive solutionstored in the storage tank 271 is supplied to the slit nozzle unit 220,and a control apparatus including a plurality of sensors 295A˜295E and aplurality of valves 290 and 280A˜280H. The supply apparatus furtherincludes a pumping unit such as a pump 272 for allowing thephotosensitive solution to be sprayed by applying constant pressure tothe photosensitive solution being supplied from the storage tank 271 tothe slit nozzle unit 220.

A buffer tank 275 is installed between the pump 272 and the storage tank271 in order to maintain a constant pressure in the pump 271 and toremove bubbles. A level sensor 290 for measuring the amount of residualphotosensitive solution is attached to the buffer tank 275.

When the level sensor 290 of the buffer tank 275 detects a shortage ofthe photosensitive solution, it sends a signal to a control apparatus(not shown). The control apparatus, in turn, sends the signal to aneighth valve 280F to allow clean and dry air to be introduced to thestorage tank 271, thereby introducing the photosensitive solution withinthe storage tank 271 to the buffer tank 275.

Then, when the first and second valves 280A and 280B are opened and thesixth, third and fifth valves 280F, 280C and 280E are closed, the pump272 draws the photosensitive solution in the buffer tank 275 to the pump272.

A filter 270 is installed between the buffer tank 275 and the pump 272,and a speed at which the photosensitive solution passes through thefilter 270 is set to be as slow as possible within a range of 0.1cc/s˜1.0 cc/s in order to improve efficiency of the filter 270. Becausethe filter 270 is installed between the buffer tank 275 and the pump272, impurities may be more effectively prevented from being introducedto the pump 272 as compared to the case where the filter 270 isinstalled between the buffer tank 275 and the storage tank 271.

Because the filter 270 is disposed downstream of the buffer tank 275 andthe buffer tank 275 does not have an air passage (which exists in thefirst embodiment), contamination and gelling of the photosensitivesolution may be more effectively avoided.

When the pump 272 completes the intake operation, positive pressure isapplied to the pump 272 by the storage tank 271. To release thepressure, the eighth valve 280H is opened so that the interior of thestorage tank 271 is in an atmospheric state. Then, the first valve 280Aand the second valve 280B are closed.

If the positive pressure of the pump 272 is not released and bubbleswithin the pump 272 and the filter 270 are to be removed, when thefirst, second and third valves 280A, 280B and 280C are closed, thefifth, sixth and seventh valves 280E, 280F and 280G are opened for apredetermined period of time (for about 1 seconds˜10 seconds). Becausethe seventh valve 280G is connected to a drain, the positive pressure ofthe pump 272 is released and, simultaneously, the bubbles within thepump 272 and the filter 270 are removed.

If the valves 280E˜280G are opened for an excessively long period oftime, low pressure is applied to the interior of the pump 272 bypotential energy because the drain is commonly placed at a lowerposition than the pump 272, which may cause introduction of bubbles intothe pump 272 and the filter 270. If the pump 272 and the filter 270 arefilled with bubbles, variations in the pump discharge amount may becaused resulting in defects.

Therefore, a discharge buffer tank (not shown) is mounted to the drainat the same elevations as the pump 272, and a drain of the dischargebuffer tank is closed to thereby release the low pressure of the pump272.

In such a manner, the internal pressure, namely, the intake amount maybe always constantly maintained. Thus, the pump discharge amount isaffected only by pump performance regardless of a line and ambientconditions.

The discharge of the photosensitive solution from the nozzle 222 isperformed in a state where the third valve 280C is opened and the restof the valves are closed during discharge operation of the pump 272.

Also, bubble discharge from the nozzle 220 may be performed by the pump272 as in the aforementioned first embodiment, but the bubbles may bemore quickly and conveniently discharged if clean and dry air isinjected into the storage tank 271 in a state that the first, second,third and fourth valves 280A, 280B, 280C and 280D are opened.

In addition, the supply line 276, the pump 272 and the slit nozzle 222are washed by filling the storage tank 271 with washing solution andthen pressurizing with clean and dry air when the seventh valve 280G isclosed and the rest of the valves are opened.

Also, supplying photosensitive solution to the nozzle 222 after thewashing is performed in the same configuration as washing.

Accordingly, the bubble discharging process for the nozzle 222, thewashing process for the pump 272 and the nozzle 222, and a process forfilling photosensitive solution in the nozzle 222 after the washing maybe performed more easily and quickly.

Unlike the first embodiment, the buffer tank 275 in accordance with thepresent embodiment has no air passage, and the storage tank 271 ispressurized by directly injecting air or nitrogen thereto, so that thewashing and the photosensitive solution supplying process may be moreeasily and quickly performed. In the apparatus for supplyingphotosensitive solution in accordance with the first embodiment, becausean air passage is installed at a buffer tank, washing solution orphotosensitive solution is discharged to the air passage of the buffertank when a storage tank is pressurized directly by the air andnitrogen. In the apparatus in accordance with the first embodiment,direct pressurization using air and nitrogen cannot be used, and thewashing and supplying of the photosensitive solution can be performedonly by a pump. Thus, it takes a long to perform such operations andconvenience of the operation is degraded.

Although not shown in the drawing, a unit for regulating the pressure ofthe clean and dray air, such as a vacuum regulator may be used inaddition to or in place of a general pressure regulator. If the vacuumautomatically and separately regulates the pressure for normallydischarging photosensitive solution through the nozzle 222, the pressurefor washing, and the pressure for discharging bubbles of the nozzle 222,the efficiency may be greatly improved.

Pressure sensors 295A˜295E are respectively installed at the storagetank 271, the buffer tank 275, the pump 272, and the slit nozzle unit220. When a reference pressure value is set the discharge of thephotosensitive solution is made based on the reference pressure value,so that the degree of coating may be visualized and the precision ofcoating through feedback control may be improved.

The first pressure sensor 295A checks the pressure of the storage tank271 to thereby check the pressure at the time of supplyingphotosensitive solution to the pump 272, check the pressure at the timeof changing the storage tank pressure to atmospheric pressure, and checkthe pressure of the atmospheric state, thereby improving precision ofphotosensitive solution transfer to the pump 272, controlling a transferspeed of the photosensitive solution and thusly improving efficiency ofthe filter 270.

Also, the second pressure sensor 295B monitors the internal pressure ofthe pump 272 and compares the pressures for intake, stoppage, anddischarge to a predetermined reference value. The second pressure sensor295B also enables feedback control to be performed through a controlapparatus based on the comparison result, thereby improving dischargeprecision and sensing beforehand possibilities of defect-occurrence.

Also, the third pressure sensor 295C and the fourth pressure sensor 295Dmonitor discharge pressure of the nozzle 222. In the present embodiment,two pressure sensors 295C and 295D are used for monitoring dischargepressure of the nozzle 222, but the present invention is not limitedthereby and only one pressure sensor may be used. In particular, onepressure sensor may be installed at one side of the slit nozzle unit220.

In the present embodiment, by installing the pressure sensors 295C and295D at both sides of the slit nozzle unit 220, the sensors 295C and295D can monitor the pressure both when the nozzle 222 does not performthe discharge operation and when the discharging operation is performed.Particularly, blockage of the nozzle 222, variations in the pumpdischarge amount, changes in the amount of photosensitive solutionwithin the nozzle 222 due to a capillary phenomenon can be detected. Ifa detected value is different from a predetermined reference value,feedback control is performed through a control apparatus. Also, ifcompensation by the feedback control is not made and there is apossibility of defect-occurrence during a process, a user may benotified of those results.

By monitoring the pressure of the buffer tank 275, the fifth pressuresensor 295E can improve the precision when the photosensitive solutionis supplied.

As described above, the slit coater having an apparatus for supplyingcoating solution may apply a uniform amount of photosensitive solutiononto a surface of a large substrate where contamination of thephotosensitive solution is minimized and a filtering function isutilized as much as possible, thereby improving productivity.

Also, the present invention may improve the operability, ease, andconvenience of a washing process and a subsequent process of injectingphotosensitive solution to a slit nozzle after the washing process.

Also, because the present invention provides a pump or a unit fordetecting pressure of the nozzle so as to monitor and control adischarge state of the photosensitive solution, productivity andefficiency may be improved.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, but rathershould be construed broadly within its spirit and scope as defined inthe appended claims, and therefore all changes and modifications thatfall within the metes and bounds of the claims, or equivalents of suchmetes and bounds are therefore intended to be embraced by the appendedclaims.

1. A method for fabricating an LCD device using a slit coater, themethod comprising: providing a table on which an LCD substrate ismounted; and applying a coating solution onto the substrate using a slitnozzle, wherein the coating solution is supplied to the slit nozzle by acoating solution supply apparatus including a storage tank configured tostore the coating solution, a pump that supplies the coating solutionstored in the storage tank to the slit nozzle unit through a firstvalve, and a sealed buffer tank in fluid communication with the pump andthe storage tank, a second valve placed between the buffer tank and theslit nozzle unit, a drain placed between the second valve and the buffertank and a third valve placed between the drain and the buffer tank; andremoving air bubbles through the drain in a state that the second valveor third valve is opened and air is injected into the storage tank. 2.The method of claim 1 further comprising providing a pressure controlsystem that comprises: a first pressure sensor configured to monitor thestorage tank pressure when supplying coating solution to the pump, andwhen venting the storage tank to atmospheric pressure; and a secondpressure sensor configured to monitor the internal pressure of the pump.3. The method of claim 2, wherein the pressure control system furthercomprises a third pressure sensor configured to monitor the dischargepressure of the slit nozzle unit, and wherein the third pressure sensoris configured to monitor the pressure when the slit nozzle unit is idleand when the slit nozzle unit performs a solution discharge operation.4. The method of claim 1 further comprising providing a filter in fluidcommunication with the buffer tank and the pump, wherein the filtersubstantially removes impurities from the coating solution introduced tothe pump.
 5. The method of claim 4, wherein the filter resides upstreamfrom the buffer tank.
 6. The method of claim 4, wherein the filterresides downstream from the buffer tank.
 7. The method of claim 4further comprising providing a level sensor configured to measure theamount coating solution in the buffer tank.
 8. The method of claim 1further comprising providing: a pressure sensor that monitors thepressure of the pump; and a fourth valve in a line coupling the pump tothe buffer tank that opens to release a rise in pressure in the pumpbeyond a predetermined pressure limit.
 9. The method of claim 1 furthercomprising providing a driving unit for moving one of the slit nozzleunit or the table in a predetermined direction.